Hybrid vehicles are driven by multiple powerplants including, but not limited to an internal combustion engine and an electric machine. The electric machine functions as a motor/generator. In a generator mode, the electric machine is driven by the engine to generate electrical energy used to power electrical loads or charge batteries. In a motor mode, the electric machine supplements the engine, providing drive torque to drive the vehicle drivetrain.
In hybrid electric vehicles, the engine is often stopped and started to improve fuel economy. Acceleration and deceleration of the engine crankshaft should be controlled during engine stop and starts to reduce driveline oscillations and other vibration inducing events that diminish the vehicle drivability. The crankshaft should also be parked in a desirable rotational position to further improve the stop-start characteristics of the engine.